求2/(1*7)+2/(7*13)+2/(13*19)+...+2/(145*151)=?,
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求2/(1*7)+2/(7*13)+2/(13*19)+...+2/(145*151)=?,
求2/(1*7)+2/(7*13)+2/(13*19)+...+2/(145*151)=?,
求2/(1*7)+2/(7*13)+2/(13*19)+...+2/(145*151)=?,
2/(1*7)=1/3*(1/1-1/7)
2/(7*13)=1/3*(1/7-1/13)
…………
2/(1*7)+2/(7*13)+2/(13*19)+...+2/(145*151)
=1/3*(1/1-1/7+1/7-1/13+1/13-1/19+……+1/145-1/151)
=1/3*(1-1/151)
=50/151
原式 =2/1×7+2/7×13+2/13×19+...+2/145×151
=1/3×(6/1×7+6/7×13+6/13×19+...+6/145×151)
=1/3×(1-1/7+1/7-1/13+1/13-1/19+...1/145-1/151)
=1/3×(1-1/151)
=1/3×150/151
=50/151
原式=2*1/6(1-1/7+1/7-1/13+1/13-1/19+……+1/145-1/151)
=2*1/6(1-1/151)
=1/3*150/151
=50/151
哇!现在的小学生真不容易,这是高中的题目啊